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The quiet field of life-cycle assessments hits the mainstream, measuring the environmental impact of what we make.

Who you gonna call when your advertising agency wants to become carbon neutral? New York agency PHD contacted civil engineering professor Arpad Horvath of the University of California, Berkeley. And when you need to know the carbon footprint of your half-gallon of milk? Aurora Organic Dairy called a chemical engineer, University of Michigan professor Greg Keoleian.


For decades, a coterie of engineering academics has quietly toiled to establish the field of life-cycle assessments, an accounting of the environmental impact of a product, service, or industry. Today, these experts are suddenly in great demand as "carbon footprint" becomes a watchword and policymakers, corporate leaders, and consumers awake to the upstream and downstream effects of each action they take. Soon, assessments may become an economic or even legal necessity as governments struggle to curb climate-altering pollutants.

At Carnegie Mellon University, life-cycle assessment specialist Scott Matthews says he's now pestered a couple of times a week by companies interested in measuring their carbon footprints. "It was nice living in obscurity for 13 years when nobody knew anything about life-cycle assessment," he quips. But in general, specialists in this field are pleased to find their moment in the sun. "The time for life-cycle assessments has come," says Berkeley's Horvath. "In the future, no economic or environmental decision will be made without consideration of the life cycle of things."

Much of the work occurs outside the aegis of engineering departments, within such research groups as Carnegie Mellon's Green Design Institute, the University of Michigan's Center for Sustainable Systems, and Berkeley's Consortium on Green Design and Manufacturing. Economists, agriculturalists, industrial ecologists, and other academics have helped lay the foundations for life-cycle assessments. Interdisciplinary cooperation is "an absolutely essential part of what we do," says Horvath.

But engineers are at the core of the field. Keoleian, who co-directs the Center for Sustainable Systems at the U of M's School of Natural Resources and Environment, reckons that most of his researchers have at least an engineering bachelor's, if not a master's, degree. With engineers' background, "we're not uniquely qualified, but we sure as heck are qualified," says Bruce Dale, a Michigan State University chemical engineer known for his analyses of the footprints of biofuels. Adds Dale, "There's no question that life-cycle assessment is a growth opportunity for engineers."

Engineers of All Stripes

Within engineering, life-cycle experts hail from a wide variety of sub-fields: environmental, civil, industrial, and chemical. The latter probably make up a plurality. "Doing mass and energy balances on industrial processes is the foundation of chemical engineering," says David Allen of the University of Texas. "It's what we're particularly adept at and trained for."

Before the rise of life-cycle assessment, companies tended to look at the energy consumption, emissions, and waste of their own production processes while ignoring environmental impacts upstream and downstream. This is a mere "toe print," in the words of Matthews, not a complete footprint. Direct emissions of greenhouse gases by an industry's factories and vehicles account, on average, for only 14 percent of its life-cycle greenhouse-gas emissions. And yet, determining just the toe print can be an exhausting exercise. When members of a University of Michigan team calculated detailed life-cycle assessments for Steelcase office furniture, they had to tabulate the number of seconds each part spent on each machine on the assembly line and the electricity, compressed air, and water consumed by those individual machines in order to calculate the impact of every part in a chair or desk. A more streamlined, if less precise, procedure is to allocate the total emissions of a plant to its various products according to value or weight. Each procedure yields different results. Says Matthews, "The common thread of the research is: 'Well . . . it depends.'"


Examining the Supply Chain

More guesswork comes in when looking upstream to add the impact of raw materials and suppliers. But this step is critical. "Once you involve the supply chain, you can get a very different outcome, often the opposite of what we have assumed is true," says Horvath. For example, many shoppers are convinced that the miles their food travels to the store account for a large proportion of its impact on the planet. But Carnegie Mellon engineers found that transport from the producer to the grocery store accounts for only 4 percent of life-cycle greenhouse gas emissions from our food. The most significant emissions are traced back to the farm itself, particularly to methane-burping cattle and sheep.

To measure upstream impacts, analysts usually rely on databases that provide average consumption and emissions for a wide variety of inputs. Carnegie Mellon's innovative Economic Input-Output Life Cycle Assessment tool ( gives the estimated cost to the environment per $1,000 spent on bauxite, banking, and 500 other commodities and services. Some of the most comprehensive databases are sold by European companies, which restrict the use of their data with non-disclosure clauses.

For a complete life-cycle inventory, an assessment must also look downstream, estimating use and life span, recycling, and waste disposal. "From our research, looking at buildings, looking at autos, looking at appliances, we find a majority of greenhouse gases are actually associated with the use phase of a product," says Keoleian.

This full inventory takes a life-cycle assessment through only its first stage. The next step is to lump the data into useful categories. Carbon dioxide, methane, and nitrous oxide emissions, for example, are grouped into greenhouse gas emissions. The quantities of the more potent gases, methane and nitrous oxide, are multiplied to come up with a single figure for global-warming potential. Methane is 25 times more potent than CO2; nitrous oxide is 298 times more potent. A similar consolidation can be accomplished for smog-forming emissions, acid-rain precursors, ozone-depleting chemicals, toxics, water pollution, solid waste, energy consumption, and other categories.

How to Package Yogurt

Finally, an analysis should recommend ways to mitigate environmental impacts. A life-cycle assessment for Stonyfield Farms yogurt by Keoleian suggested that the company eliminate polypropylene lids from its packaging and open up a plant in the western United States to reduce transportation emissions. Stonyfield Farms implemented both recommendations.

As satisfying as it may be to work directly with a company and see immediate results, university engineers emphasize that they choose work that also explores broader research questions, develops new methods, or relates to public policy. "Being in academia, we're interested in creating new knowledge," says Keoleian, "not just doing a routine study." Academics have made their mark by simplifying the arduous task of creating assessments. Horvath created a calculator used by many transportation departments to analyze the life-cycle impacts of different road-building materials. Says the Berkeley professor, "Our impact on changing the world is a lot more substantial if we create tools."

After many years spent honing the methods for creating comprehensive life-cycle assessments, some experts are disappointed that the process achieved celebrity only when scaled down to a single measurement: the carbon footprint. Leaving aside water consumption, toxic emissions, and other impacts is "a wasted opportunity," says Horvath: "Talking exclusively about carbon is myopic." Matthews also worries that the trend of marking consumer products with carbon footprint labels will distract from more fundamental issues. "Saving a gram or two by buying this brand or that brand is missing the point," notes the Carnegie Mellon engineer. "If the carbon footprint of your household is 50 tons, that gram is not something you should be worrying about," he continues.

An Explosion of Work

But others are pleased that attention to carbon footprints is arousing a vital awareness among companies, governments, and consumers. "You've got to come up with a measurement before you can seek improvement," says Carnegie Mellon's Chris Hendrickson. "This is the way we get a handle on our greenhouse gas emissions." Besides, Keoleian notes, not only is carbon dioxide a decent proxy for other air pollutants and energy consumption; its influence on the global climate makes it well-suited to life-cycle assessments.

Whether they want it or not, life-cycle assessment experts face an explosion of work in carbon footprints as governments begin to clamp down on greenhouse gases. "It could really be a big revolution for the field," says Eric Williams, an assistant professor of civil and environmental engineering at Arizona State University. With a cap-and-trade system on Washington's agenda, "you need to understand what your carbon footprint is and what your supply-chain carbon footprint is," explains Hendrickson, "because all of those costs are going to roll up though the supply chain to affect you."

The California Carbon Labeling Act of 2009, under debate in the state assembly, raises the prospect of a new surge in carbon-footprint measurements for consumer products. Horvath marvels at the scope of the task. "There are a million-and-a-half distinct products in our retail system; trying to find a footprint for all of them is a big job."

Life-cycle assessments may also keep engineering academics busy beyond the office. Sometimes the methodology follows them home. "When looking at replacing windows or an appliance, I look at the life cycle," says Keoleian. "It can bog down our purchasing decisions," he admits. "I drive my wife crazy with decisions about products."

Don Boroughs is a freelance writer based in South Africa.




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